The libido injection that claims to go one better than Viagra

Scientists claim to have discovered the secret of sexual desire in a breakthrough that could change millions of lives around the world.

They are developing a 'wonder pill' to generate sex drive in both women and men who struggle with their libido.

The medication could also have the potential to boost fertility rates and is believed to have the side-effect of encouraging weight-loss.

If successful, it could outsell the market-leading impotence drug Viagra, as it bolsters the brain's desire for sex, whereas Viagra boosts only physical capability.

Loss of libido affects more than a third of women and up to one in six men, but experts report a growing problem with a decline in sexual desire among stressed-out males.

The pill would use a hormone that releases Type 2 gonadotropin, which drives the reproductive system in animals and humans.

Tests on animals have proved successful and researchers at the Medical Research

Council's Human Reproductive Sciences Unit in Edinburgh are working on an equivalent for humans.

Professor Robert Millar, the unit's director, initially thought the drug would work only on women - but now believes there is no reason for it not to work on men and is planning further tests.

Professor Millar said that when female musk shrews and marmoset monkeys received injections in laboratory tests, they displayed classic mating behaviour towards their male counterparts.

In musk shrews this was shown by 'rump-presentation and tail-wagging' and in monkeys it included 'tongue-flicking and eyebrow-raising'.

An unexpected side-effect was that the laboratory animals ate significantly less food than usual - in some cases a third less than their usual daily diet.

In the animal tests, the drug could at first be injected only into the brain. But they have now been able to inject the drug into the bloodstream instead - a crucial move towards making a human version of the drug that could be released for a global mass market.

In time, they hope to produce the drug in pill form and believe it would make Viagra, the tablet that has so far been used by 27million men around the world, redundant.

Professor Millar said: 'This drug would cut out the need for Viagra completely - Viagra does not produce desire, it simply leads to an erection but not to the desire for sex.

'This drug would arouse and produce the desire for sex at the same time, in both men and women.

'It is very exciting that we have made so much progress, as the stimulation of libido would mean a great deal to a huge number of people.

'One of the next steps will be to produce a pill, as at the moment we can only inject, although surveys show many people, particularly men, are happy to inject and diabetics seems to manage it without too much trouble.

'Certainly we want to produce an oral form of this so that it could be taken very easily by both men and women.'